The present invention relates to a device for measuring in three dimensions a topographical shape of an object, said device comprising an arrayed confocal imaging system having a light source provided for illuminating said object and a light path diverging optical element, provided for diverging a path of illuminating light output by said light source and a path of reflected light reflected by said object, said confocal imaging system further comprises a confocal topographical mask provided for converting illuminating light coming out from said light path diverging optical element into an array of small spots, said confocal imaging system further comprises a confocal objective provided for orienting said illuminating light towards said object and said reflected light towards said confocal topographical mask in order to form a confocal image, said device further comprises a photoelectric sensor member provided to receive said reflected light having passed said confocal topographical mask and deflected by said light path diverging optical element and to convert the latter light into an intensity value, said device comprising also a scanning member on which said confocal topographical mask is mounted, said scanning member being provided for moving said confocal topographical mask over successive positions over a predetermined distance in order to modify a relative distance in a predetermined direction between said object and the object-position-in-focus, said device further comprises an image processor connected to said photoelectric sensor member and provided for forming a confocal response signal and calculating said object shape from said confocal images acquired at different relative distances in said predetermined direction between said object and the object-position-in-focus by said photoelectric sensor member, said confocal objective being provided for mapping at successive object-position-in-focus said array of small spots output at said successive positions.
The invention also relates to a method for measuring in three dimensions a topographical shape of an object.
Such a device and method are known from EP-A-0679864. In the known device and method the light source outputs a path of illuminating light which crosses the light path diverging optical element formed by a hologram and a lens array and reaches the confocal topographical mask comprising a pinhole array. The path of illuminating light which is formed by an array of small spots after passing the mask, ends at the object to be measured. At the location of the object the incident light spots are reflected and the reflected light crosses the mask to reach the light path diverging element. The latter deflects the reflected light towards the photoelectric sensor member, where the incident light is sensed and further processed by the image processor in order to determine a three dimensional shape of the considered object. In order to determine the third dimension, means are provided for modifying the relative distance in the z-direction between the object and the object-position-in-focus. In the known device, the latter means are formed by a set-up comprising a scanning member on which the confocal topographical mask, the light path diverging optical element, the sensor members and the confocal objective are mounted. The movement of the whole set-up in the z-direction causes the object-position-in-focus to shift in the z-direction over a predetermined distance. Accordingly the relative distance in the z-direction between the object and the object-position-in-focus changes, thus enabling to determine the third dimension.
A drawback of the known device and method is that the confocal topographical mask as well as the light path diverging optical element, the sensor members and the confocal objective are all moved together in the z-direction in order to modify the relative distance between the object and the object-position-in-focus. The movement of such a relatively heavy set-up requires some power and is not the most appropriate choice for high speed on-line determination.